This invention relates to molded fastener members useful for engaging loops and the like.
In hook and loop fasteners, typically an extensive field of molded hooks aligned in adjacent rows on one half of the fastener, the xe2x80x9chook elementxe2x80x9d, engages mating loops or anchored fibers on the other half of the fastener, the xe2x80x9cloop element.xe2x80x9d
Fastener members of a molded hook element typically are integrally formed with the base, each including a stem extending from the base to a head with a crook which overhangs the base. Often the mold cavities in which the hooks are formed have no moving parts, the hook fastener elements being pulled from the mold cavities by resiliently distorting the solidified crook portions of the hooks. For molding a running strip of such a hook element, a rotating mold roll is employed. For discrete items, cyclable injection molding techniques are employed. Typically in either case, the mold is formed of a stacked series of plates, with the overhanging crooks of the hooks confined to face in the direction of the planes of the mold plates.
One characteristic of fastener components is the shear strength of engagement between them. This refers to their ability to resist disengagement when subjected to a force acting along the plane defined between the mating faces of the hook and loop elements. The shear strength often determines the strength limit of the attachment. In many applications, the fastener is applied with the hook elements aligned to face in a first direction, but the shear load applied to the fastener component is in a direction that is perpendicular to, or at a substantial angle to, the direction in which the hooks face. For example, hook fastener components in some disposable diapers face in a direction generally parallel to a baby""s waistline, yet the forces on the fastener caused by motion of the baby""s legs are substantially perpendicular to the waistline.
The present invention features a fastener for engaging loops, which includes a base and a field of fastener elements molded with and extending from the base. The fastener elements are constructed to engage loops of a mating loop component to form a releasable fastener and include hooks which define crooks for capturing loops. Spikes are interspersed among the hooks and extend at an acute angle from the base to at least the height of the crooks above the base. The fastener elements are arranged in rows, with a first set of rows comprising hooks and a second set of rows comprising spikes.
In accordance with another feature of the invention, the hooks extend in a first direction along the base, and the spikes extend in a second direction along the base.
In accordance with another feature of the invention, the fastener has spikes with an engagement tip for capturing loops extending at an acute angle from the base. Latch stems are located on the base adjacent to the spikes and beneath the engagement tip to cooperate with the spike to capture the loops.
In accordance with another feature of the invention, the fastener has pairs of adjacently opposed structures on the base. The pairs include a first structure and a second structure with an engagement tip for capturing loops. The engagement tip has a first position located above the first structure, and a second position located beneath the first structure.
In accordance with another feature of the present invention, there is provided a mold for producing a fastener. The mold includes a set of mold plates which have hook mold plates and spike mold plates. The hook mold plates have hook mold surfaces for producing hooks which are molded with and extend from a base. The hooks define crooks for capturing loops of a mating loop component. The spike mold plates have spike mold surfaces for producing spikes which extend at an acute angle from the base.
In accordance with another feature of the present invention, there is provided a method for forming a loop engaging fastener. The method includes providing a mold for the fastener which has a set of mold plates. Hook mold plates with hook mold surfaces for producing hooks are provided, along with spike mold plates having spike mold surfaces for producing spikes. Moldable resin is delivered to the mold such that the resin is forced into the mold surfaces, where it is solidified into hooks and spikes which are then removed from the mold.
Another feature shown is a mold roll for forming a fastener component, the mold roll having mold cavities open to the outer surface of the roll for forming a field of fastener elements supported by a base, by application of moldable resin under pressure against the outer surface of the mold roll in the manner to fill the cavities open to the outer surface and to form the base on the outer surface of the mold roll, characterized in that the mold roll comprises an outer mold ring placed over an inner mold ring, the outer mold ring having a set of mold cavities that extend from its outer surface to its inner surface and the inner mold ring having mold cavities aligned with respective mold cavities in the outer ring, whereby moldable resin on the outer surface of the mold roll can flow from the mold cavities of the outer ring into the mold cavities of the inner ring, the cavities of both rings constructed to cooperate to form the fastener elements. A method of forming a fastener component employing this mold roll comprises continuously applying moldable resin under pressure to the outer surface of the roll as the roll is turned, preferably in which a nip is formed between the mold roll and a pressure roll and molten resin is introduced into the nip as the rolls counter-rotate, or in which an extruder nozzle extrudes molten resin under pressure against the surface of the mold roll as the roll turns.
In preferred embodiments of these features the mold roll or the method form fastener elements that have outer end portions shaped to engage fastener loops.